Portable generators are often operated under variable load conditions. However, operating portable generators under variable load conditions can present a number of problems. For instance, diesel engines used in portable generators are susceptible to problems associated with light-load conditions. More specifically, when a portable generator with a diesel engine operates at a light-load condition, fuel within the diesel engine remains unburned. The unburned fuel can form deposits (e.g., tar or carbon) that can collect within various parts of the engine, such as the exhaust pipes. When the deposits collect within the various parts of the engine, this is known as “wet stacking.”